From 389cbaf611f47ce375e7e9ea446cd67175c082ad Mon Sep 17 00:00:00 2001
From: Umesh Kadam <43408418+TheUmeshKadam@users.noreply.github.com>
Date: Tue, 23 Dec 2025 18:43:40 +0530
Subject: [PATCH] feat: support multiple WebSocket sub-protocols in MQTT
 connection

Allow custom WebSocket sub-protocols to be specified via opts.wsOptions.protocol
(comma-separated). Custom protocols are now included alongside the default MQTT
protocol during WebSocket connection negotiation.

- Changed from single protocol to array of protocols
- Parse custom protocols from opts.wsOptions.protocol if provided
- Maintain backward compatibility by always including MQTT protocol
---
 mqtt.js | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/mqtt.js b/mqtt.js
index f8c9fe7..e53e068 100644
--- a/mqtt.js
+++ b/mqtt.js
@@ -4726,14 +4726,19 @@ function createWebSocket (client, url, opts) {
 }
 
 function createBrowserWebSocket (client, opts) {
-  const websocketSubProtocol =
-  (opts.protocolId === 'MQIsdp') && (opts.protocolVersion === 3)
+  let websocketSubProtocols = [];
+
+  if (opts != undefined && opts.wsOptions !== undefined && opts.wsOptions.protocol !== undefined) {
+    websocketSubProtocols = opts.wsOptions.protocol.split(',');
+  }
+  
+  websocketSubProtocols.push((opts.protocolId === 'MQIsdp') && (opts.protocolVersion === 3)
     ? 'mqttv3.1'
-    : 'mqtt'
+    : 'mqtt');
 
   const url = buildUrl(opts, client)
   /* global WebSocket */
-  const socket = new WebSocket(url, [websocketSubProtocol])
+  const socket = new WebSocket(url, websocketSubProtocols)
   socket.binaryType = 'arraybuffer'
   return socket
 }
@@ -18671,4 +18676,4 @@ module.exports = {
 };
 
 },{}]},{},[17])(17)
-});
+});
\ No newline at end of file